The present invention relates to the dewatering of gluten during corn processing. The wet milling processing of shelled corn is employed to obtain staple products such as corn oil, dextrose, corn syrup, high fructose corn syrup, dextrins, dry starches and feeds. The principle steps in the wet milling of corn include steeping, milling, recovering and processing. During the steeping operation, corn kernels are softened by soaking in a hot dilute solution of sulfurous acid (i.e., sulfur dioxide). The softened kernels are then passed through grinding mills and separators where the germ is removed and the starch and gluten are separated from the coarser hull and fibers. The starch is then separated from the gluten which is added to the fibrous material and processed into a high protein animal feed. The starch is recovered as dry starch or further processed into dextrose and fructose. The sulfurous acid steepwater initially used to soften the corn contains solubles which are recovered for use in feeds. The steepwater solids are recovered by evaporation and drying. The solids recovered from evaporating and drying the steep water are used as additives to livestock feeds to enhance their nutritional value.
Processing of the gluten also involves dewatering. Typically, the gluten stream is held in a light gluten storage tank prior to pumping to a bowl type centrifuge where the first step of dewatering begins. The gluten slurry from the centrifuge, called heavy gluten, is then sent to a vacuum dewatering system where the second step in the dewatering occurs. The gluten cake from the vacuum dewatering system is transported by auger to a dryer for final dewatering.
In the gluten dewatering process, the second step of vacuum dewatering is often the limiting factor in gluten recovery. The time necessary to teach the required gluten moisture content coupled with the potential for blinding of the filter media limits the throughput of gluten in this area. The present invention is directed to a process for decreasing the dewatering time and inhibiting blinding of the filter media in gluten dewatering.
The use of surfactants in grain processing is known. U.S. Pat. No. 3,362,829 discloses a process for coating powdered vital wheat gluten with a nonionic hydrophilic lipid selected from the class consisting of monoglycerides, salts of lactylic esters of fatty acids, polyoxyethylene stearate and stearyl monoglyceridyl citrate. The coating of the powdered wheat gluten with such nonionic hydrophilic lipids is disclosed as controlling wetting of the vital wheat gluten upon hydrogenation. The use of polyoxyethylene sorbitan monostearate in combination with hydrophilic lipids is also disclosed. The surface active agent, i.e., polyoxyethylene sorbitan monostearate is included as an aid for the initial dispersion of the vital wheat gluten.
U.S. Pat. No. 3,880,824 discloses a gluten/lipid complex and process for preparing a gluten/lipid complex in which vital wheat gluten complexes with lipids are prepared which are resistant to particle cohesion. A finely divided vital wheat gluten is reacted with ionic and nonionic fatty substances selected from the group consisting of fatty acid chlorides, fatty monoglycerides, lactylic esters of fatty acids, phospholipids and sorbitan fatty acid esters in the presence of a mild base catalyst. The phospholipids and lactylic esters of fatty acids yield comparable complexes in an acidic environment.
U.S. Pat. No. 4,929,361 discloses a method of controlling the fouling of heat transfer surfaces in evaporators and concentrators employed in wet corn milling which comprises treating the wet corn solution with a nonionic surfactant such as polyoxyethylene 20 sorbitan R.